Under a plan announced Tuesday, city planners would review the design of all new town-home developments. If the City Council approves the change, developers say it would devastate the town-home industry and wipe out a wide swath of affordable homes.

In addition to the new level of review, Nickels proposed code changes to address recurring complaints throughout the city: large windowless walls butting up against sidewalks, the missing front door, towering fences and a giant paved auto court.

The proposed changes come as Seattle continues to struggle with a lack of affordable housing for median-wage earners. The review process now takes six to nine months. The city hopes to shorten the additional wait time to one or two months, which would add some cost to development.

Still, he said, “This leaves the door open for affordable housing, but does it in a way that adds to, rather than detracts from the neighborhood.”

Just last week, the City Council approved the mayor’s proposal to expand a tax break for developers who set aside affordable units in new buildings. The 2009 rent levels under that plan start at $1,115 a month for a studio, which the city says is affordable to a single person who next year will earn $46,705, or 80 percent of the median income of $58,380.

Buying a town home is how many renters have found their way into homeownership. Over the past eight years, more than 8,000 town homes have received permits in Seattle, according to Councilmember Sally Clark’s office.

This year, 668 town homes have been sold in the city, compared to 2,152 single-family homes, according to a Windermere analysis of Northwest Multiple Listing Service data. At a median price of $392,500, a town home costs $100,000 less than the typical single-family home in Seattle this year, and close to $60,000 less than the typical home in King County.

The mayor also proposed changes to the multifamily-building code, calling for environmentally friendly landscaping such as a green roof, more doors and windows on walls facing the street, a pedestrian entry from the street, lower fences and less — even no — parking in projects near mass-transit hubs.

“It’s a good start,” said Vlad Oustimovitch, an architect, former design-review board member and outspoken critic of what he calls “cookie-cutter town homes.” “The current situation was really so out of control that any changes are really welcome at this point.”

Upon hearing of the mayor’s proposal, developers were most upset about the added design review.

Many builders said design review — now required for larger projects — will make town homes more expensive because they will take longer to build and sell. It has become common for developers to avoid review by seeking permits for smaller, adjoining projects.

Miklos Kohary, who built 160 town homes in the city last year, said the mayor’s “insane” proposal would add $30,000 to $40,000 to each home. He now spends that much on loan payments, he said, waiting for building permits to clear with the city, which takes seven to 10 months.

“We were doing what was the objective of the mayor: affordable housing,” Kohary said. “My average buyer ranged from 22, 23 to 35. These were all young people who didn’t want to have a big garden and a house.

“[City officials] either want housing or they don’t. If they want housing, this is insane.”

Kohary, who built a widely criticized cluster of town homes near North 85th Street and Stone Avenue North, said the mayor’s architectural code changes would improve the look of town homes. But he does not understand why the city also wants a design review.

Alan Justad, deputy director for the Department of Planning and Development, said the review would allow builders to be more flexible. In some cases, city planners may even waive code requirements for better design, he said.

Hillary Viswanathan and her husband bought a town home on 21st Avenue East in Capitol Hill in 2005 for $382,000. They loved the neighborhood and her husband could walk to work.

She likes the mayor’s proposal to require a front door for houses facing the street and a lowering of the maximum fence height to four feet. She had already been thinking about making the same changes to her home.

But if their home had been priced $30,000 higher, they would have looked elsewhere. “This is an expensive housing market as it is,” she said. “Town homes are one of the only opportunities available to people who aren’t inordinately wealthy.”

Councilmember Clark, chairwoman of the land-use committee, said she appreciates the mayor’s responsiveness to neighborhood concerns, but “I don’t know that it gets at the cookie-cutter design,” she said. Nickels plans to send the legislation later this summer, and Clark says the council will take a closer look then.